The long range goal of the research is the elucidation of long range structure of DNA in certain prokaryotic and eukaryotic chromosomes and the definition of the molecular interactions which organize this structure. Specifically, we are investigating the role of certain non-histone chromosomal proteins of Drosophila melanogaster in organizing DNA packaging in interphase nuclei. We are also investigating the function of certain prokaryotic proteins in restraining toroidal supercoils in the nucleoid (chromosome) of Escherichia coli. The organization of DNA loops and domains of supercoiling in chromosomes is also being studied.